ICHNEUMONS AND THEIR ALLIES 105 



is usual for Hymenoptera which sting or bore to have a slender 

 waist. This increases the mobility of the abdomen, which is 

 sometimes extreme. Some ichneumons, when they lay their 

 eggs, bend the abdomen forwards over the back and then 

 vertically downwards ; others bend it so far under the thorax 

 that the borer reaches beyond the head. The borer can be 

 directed to almost any point ; if it is long, it may be worked 

 up and down at right angles to the body ; and there is often a 

 certain amount of side-to-side action, or a twisting motion as 

 well. Though the sting or borer is generally associated with 

 a slender waist, the slender waist does not imply a sting or 

 borer. To say nothing of narrow-waisted Hymenoptera, which 

 have lost the apparatus once possessed by their progenitors, 

 most male Hymenoptera have the slender waist, but never 

 possess either sting or borer. 



We sjiall next describe the general structure and mode of 

 life of a few well-known ichneumons. One of the commonest 

 ■ of our native species is a large orange-coloured insect (Ophion 

 luteus), which has its abdomen flattened from side to side, and 

 curved in a vertical arch to the shape of a sickle-blade. The 

 borer is short and concealed. The feelers are long and slender, 

 and do not quiver. Ophions are often yellow, sometimes 

 yellow and black, or red ; they are never marked with white. 

 Ophion luteus is 12 mm. long; some other species are longer. 

 The female Ophion seeks out leaf-eating caterpillars, which are 

 not hidden in earth or wood. She does not pierce the body, 

 but applies a sticky egg to it, and then, withdrawing her 

 abdomen, leaves the egg fastened by a long thread which 

 immediately sets hard. When the larva is hatched from the 

 egg, it bites, enters, and in the end devours its host, pupating 

 outside the dead body within a long, parchment-Kke cocoon. 

 Noctuid and Bombycine larva, and most commonly perhaps, 

 the larva of the puss-moth, are attacked by Ophion luteus. 

 Several eggs are generally laid upon one larva. 



Very different are the structure and habits of the ichneumons 

 which prey upon wood-boring larvae. Pimpla manifestator, for 

 instance, attacks the larvae of longicorn beetles and wasps in 

 the wood of trees. Its length, not including the ovipositor, is 

 30 mm. The general colour is black, but the legs are orange. 

 The abdomen is long, slender and flexible, but not distinctly 

 stalked; the borer equals in length the rest of the body. 



